1. Field of the Invention
The present invention relates to a wafer dividing method for dividing a semiconductor wafer into a plurality of individual devices, wherein a die bonding film such as a die attach film (DAF) is attached to the back side of the semiconductor wafer.
2. Description of the Related Art
A plurality of devices such as ICs and LSIs are formed on the front side of a semiconductor wafer so as to be partitioned by a plurality of division lines. After grinding the back side of the semiconductor wafer to reduce the thickness of the wafer to a predetermined thickness, the wafer is divided into the individual devices by using a dicing apparatus (cutting apparatus). The devices thus obtained are widely used in electric equipment such as mobile phones and personal computers. In recent years, it has been desired to further reduce the weight and size of electric equipment such as mobile phones and personal computers, so that thinner devices have been required. As a technique of dividing a wafer into thinner devices, a so-called dicing before grinding process has been developed and put to practical use (see Japanese Patent Laid-open No. Hei 11-40520, for example).
This dicing before grinding process includes the steps of forming a dividing groove having a predetermined depth (corresponding to the finished thickness of each device) along each division line on the front side of a semiconductor wafer and next grinding the back side of the semiconductor wafer to expose each dividing groove to the back side of the semiconductor wafer, thereby dividing the semiconductor wafer into the individual devices. By this dicing before grinding process, the thickness of each device can be reduced to 50 μm or less. However, in the case of providing a die attach film (DAF) as a die bonding film on the back side of the wafer divided into the individual devices by the dicing before grinding process, it is relatively difficult to divide the DAF along the boundaries of the individual devices, resulting in low productivity (see Japanese Patent Laid-open No. 2002-118081, for example).
Further, a technique called stealth dicing has been proposed and put to practical use (see Japanese Patent No. 3408805, for example). The stealth dicing includes the steps of applying a laser beam having a transmission wavelength to the wafer along the division lines in the condition where the focal point of the laser beam is set inside the wafer at a position corresponding to each division line to thereby form a plurality of modified layers inside the wafer along the division lines and next applying an external force to the modified layers to thereby divide the wafer into the individual devices. According to this technique, the spacing between any adjacent ones of the individual devices obtained by dividing the wafer is very small. Accordingly, in the case that a DAF is provided on the back side of the wafer divided into the individual devices, and the wafer is attached through the DAF to a dicing tape, the DAF can be easily divided by expanding the dicing tape in the radial direction (see Japanese Patent Laid-open No. 2005-223285, for example).